RT info:eu-repo/semantics/article
T1 Ionic currents in dispersed chemoreceptor cells of the mammalian carotid body
A1 Ureña, J.
A1 López López, José Ramón
A1 González, Constancio
A1 López Barneo, José
K1 Cuerpo carotídeo
K1 Quimiorreceptores
K1 Carotid body
K1 Chemoreceptors
AB Ionic currents of enzymatically dispersed type 1 and type 11 cells of the carotid body have been studied using the whole cell variant of the patch-clamp technique. Type 11 cells only have a tiny, slowly activating outward potassium cur­ rent. By contrast, in every type 1 chemoreceptor cell studied we found (a) sodium,(b) calcium, and (e) potassium currents. (a) The sodium current has a fast activation time course and an activation threshold at --40 mV. At ali voltages inactivation follows a single exponential time course. The time constant of inactivation is 0.67 ms  at  O  mV.  Half  steady  state  inactivation  occurs  at  a membrane  potential  of--50 mV. (b) The calcium current is almost totally abolished when most of the extemal calcium is replaced by magnesium. The activation threshold of this cur­ rent is at --40 mV and at O mV it reaches a peak amplitude in 6-8 ms. The calcium current inactivates very slowly and only decreases to 27% of the maximal value at the end of 300-ms pulses to 40 mV. The calcium current was about two times larger when barium ions were used as charge carriers instead of calcium ions. Barium ions also shifted 15-20 mV toward negative voltages the conductance vs. voltage curve. Deactivation kinetics of the calcium current follows a biphasic time course well fitted by the sum of two exponentials. At -80 mV the slow com­ ponent has a time constant of 1.3 ± 0.4 ms whereas the fast component, with an amplitude about 20 times larger than the slow component, has a time constant of0.16 ± 0.03 ms. These results suggest that type 1 cells have predominantly fast deactivating calcium channels. The slow component of the tails may represent the activity of a small population of slowly deactivating calcium channels, although other possibilities are considered. (e) Potassium current seems to be mainly due to the activity of voltage-dependent potassium channels, but a small percentage of calcium-activated channels may also exist. This current activates slowly, reaches a peak amplitude in 5-1O ms, and thereafter slowly inactivates. Inactivation is almost complete in 250-300 ms. The potassium current is reversibly blocked by tetraeth­ ylammonium. Under current-clamp conditions type I cells can spontaneously fire large action potentials.
PB The Rockefeller University Press
SN 0022-1295
YR 1989
FD 1989
LK http://uvadoc.uva.es/handle/10324/24724
UL http://uvadoc.uva.es/handle/10324/24724
LA eng
NO Journal of General Physiology, 1989, vol. 93. p. 979-999
NO Producción Científica
DS UVaDOC
RD 22-dic-2024